1. Field of the Invention
The present invention relates to the field of shock and vibration attenuation for media drives.
2. Background Art
High performance disk drives are finely tuned electromechanical devices. The precision necessary to allow these devices to work is proportional to their capacity to hold customer data and their ability to handle the data in volume. Disk drive performance is dependent on drive design, which includes servo algorithms, spindle and disk pack balancing, internal damping and dynamic characteristics. Disk drive performance is also influenced by the environment in which the disk drive must operate.
In an effort to reduce cost per megabyte of storage, track density, or tracks per inch (TPI), has increased. The TPI trend, along with efforts to reduce packing costs and unit footprints, has led to significant challenges regarding disk drive implementation. Obstacles presented to the industry consist of damping and attenuating the disk drive""s own internally generated vibrations, isolating the disk drive from vibrations created by neighboring disk drives, and isolating the disk drive from externally generated shocks and vibrations.
A poorly implemented disk drive mounting solution may cause various problems at a higher system level. An unconstrained, vibrating disk drive will tend to knock itself off track while performing a read or write seek. If the drive cannot successfully find the correct location to read or write on the disk surface, the disk drive must wait until the disk pack rotates around to the same location to attempt the operation again. The extra rotation results in a write or read inhibit that is treated as an error. These errors can affect the input/output speed of the individual disk drive and the system as a whole. If the problem is severe enough, the disk drive will be turned off or fenced due to its inability to read and write data. It is possible that the disk drive will be fenced due a system level mounting problem and not due to a problem with the disk drive itself. Corrective maintenance for shock and vibration induced errors will usually result in the replacement of a healthy disk drive.
Several approaches have been used in attempts to minimize the effects of self-induced vibrations, and externally induced shocks and vibrations on various disk drives. Many of these same approaches are also used with other moving-media type drives such as optical dives, magneto-optical drives, and tape drives, generically referred to as media drives.
A common shock and vibration damping approach is to attach each media drive to a system level drive tray through one or more springs. Springs provide a degree of mechanical isolation between neighboring media drives mounted in the drive tray, as well as isolation from externally induced shocks and vibrations. Springs, however, allow vibrational energy to remain in the media drive thus adding to the energy spectrum of the media drive environment. Springs also contact the media drive chassis in only a few specific locations that are selected based upon a center of mass and not based upon closeness to the vibration sources.
Resonant plates have also been incorporated in damping systems to control the frequency of vibrations present in the media drive""s chassis. The plates have a resonant frequency at which the media drive is relatively immune to vibration induced errors. Most of the vibrational energy present in the media drive""s chassis is converted to the resonant frequency by the plates. Plates by themselves, however, do not dissipate the vibrational energy. All of the energy that enters the plates eventually returns to the media drive chassis or is transferred away through the springs.
The present invention provides an improved damping mechanism and method of operation that addresses the limitations discussed above.
A system according to the invention for mounting multiple media drives includes a housing and multiple modules that are insertable into and removable from the housing. Each module is adapted to hold a media drive. Furthermore, the system includes a resilient layer disposed between the housing and the modules when the modules are inserted into the housing for attenuating shocks and vibrations. The resilient layer includes a slot for inhibiting transmission of shocks and vibrations between at least two of the modules.
A tray according to the invention for housing multiple modules includes a housing having multiple bays adapted to receive the modules, and a resilient layer attached to the housing and extending into each of the bays to attenuate shocks and vibrations. The resilient layer includes at least one slot for inhibiting transmission of shocks and vibrations through the resilient layer.
A method for attenuating vibrations between multiple media drives and a tray includes converting the vibrations into resonant vibrations at a resonant frequency in multiple plates associated with the media drives, the resonant frequency being outside an adverse frequency range for the media drives; and damping the resonant vibrations in multiple resilient layers disposed between the tray and the media drives, two of the resilient layers being positioned such that the media drives are disposed between the two resilient layers, each of the two resilient layers having at least one slot for inhibiting transmission of resonant vibrations between at least two of the media drives.